2016 Mazda CX-9

We discovered the problem by accident -- pulled out of our garage and there was a coolant puddle on the garage floor. No dashboard warnings, no overheat messages, no visible symptoms before that. That's what makes this failure mode dangerous: it loses coolant silently, and you find out from a puddle or from an overheat, not from the car telling you. A Mazda dealership confirmed the failure during a multi-point inspection by one of their master technicians (September 2026): coolant leaking from the back of the cylinder head, no signs of coolant and oil mixing, and a scan showing no history of overheating. Their recommendation is cylinder head replacement. The vehicle is available for inspection on request. This exact failure mode is a known design defect on 2016-2020 CX-9s with the 2.5T engine. Mazda itself acknowledged it -- special service program CSP11 ("Coolant Leaks at Cylinder Head Warranty Extension," NHTSA doc MC-11011136-0001, issued October 2024). That program extended the powertrain warranty to 10 years / 120,000 miles for precisely this failure, covering vehicles produced before June 2020 -- which includes this one. Here's the part that gets me: my vehicle is in the CSP11 VIN range, and the defect was diagnosed inside the program's 10-year date window. But the odometer is past 120,000 miles, so coverage was denied. The owner notification for CSP11 didn't go out until November 2024 -- to original owners. I bought this vehicle used, and never received that notice, so

Cracked head cyclinder leaking. Unsafe to drive, coolant can leak into engine if not already. They are aware of it and extended a warranty for the issue in 2024. However people like me, my coolant didn't leak until this year 2026. There have been lawsuits on this issue, but they are still failing to address this issue. They created another part to replace the defected part which costs around $6000-$7000. Yes, took it to a Mazda dealer and confirmed the issue and they can fix but cost would be out of pocket. No warning at all. The only way this was discovered was the smell of the coolant leaking.

My car have a manufacturer engine defect that the company or corporation is not willing to fix. Only because I exceeded the warranty I call them (MAZDA) an told them that it wasn't under my control the these issues happened after the warranty expire. But they still refuse to help me.

Engine revs or surges while in park, possibly faulty throttle box

The cylinder head (which involves the engine cooling system) has a known manufacturer defect that affects all year/models of the Mazda CX-9 with turbo. The manufacturing defect poses a risk to motor vehicle safety in a group of vehicles or equipment of the same design and/or manufacturer. Specifically, the overheating and failure of the engine can occur at any time, without warning. This puts my family at risk of being stranded on a roadway, particularly because my car is often driven in rural areas. The manufacturing defect is significant and is acknowledged by Mazda: Mazda has offered owners a voluntary, limited, warranty extension (CSP11) of 10 years or 120,000 miles. The voluntary warranty extension is not sufficient because it is limited in duration while the safety risk can happen at any time after the warranty extension expires. The warranty extension essentially only applies to about half of the expected lifetime of the car. NHTSA should determine that a recall and repair should be issued by Mazda that does not expire. The engine is defective, poses a safety hazard, and Mazda has fixed the engine for subsequent models (starting in 2021), so a repair is available.

I own a 2016 Mazda CX9 Touring FWD (180k miles). Today my car was diagnosed with cracked cylinder head, resulting in coolant and oil leak from the head gasket. While there is a class action settlement about it where Mazda accepted the manufacturing defect, they do not cover the engine repair/cylinder head replacement because my car's mile is over 120k. If it is a manufacturing defect, why year/mile make a difference on the responsibility of the manufacturer? Mazda obviously sold defect vehicles to their customers, and driving these vehicles under this condition is very dangerous! Now, they are expecting me to pay more than $10,000 for a vehicle priced around $6,000!

In June of 2022 I started having a strong antifreeze/engine coolant smell inside the cab of my vehicle and also outside the vehicle. I had the car checked for a radiator leak, but there wasn’t one. I took my car into my local Mazda where they found that the engine coolant was leaking into the heads of the engine. Mazda kept my car for 5 months and repaired the problem, it cost me $4000 and they had added a 12 month 12,000 mile warranty for the parts. My car is a 2016 Mazda cx-9 at the time of the repair it had 70,430 miles on it. Now a few years later I am having the same issue with the coolant smell inside the cab and outside my vehicle, it goes into the shop for diagnosis on Monday November 10,2025. The car now has 118,000 miles on it. I had purchased an extended warranty for the car at the time of purchase but it had timed out a month before I took my car in for the first repair….please Mazda stand behind your vehicles I am a senior woman with very little income and I will not be able to pay out of pocket for this repair and I CANNOT afford a new car… I would like to get reimbursed for my out of pocket on the first repair and get my car repaired this time as well under a warranty.

Cylinder head crack. Combustion gasses leaking into coolant causing overheat. Combustion gasses bleeding into oil causing excessive crankcase pressure.

The contact owns a 2016 Mazda CX-9. The contact stated that while driving approximately 45-50 MPH, the vehicle suddenly lost motive power with white smoke coming from the front of the vehicle. The contact was able to get to the side of the road to inspect the vehicle and became aware that there was coolant splattered all over the engine compartment. The failure had occurred twice. The “WRENCH” symbol was displayed with the “Service Vehicle” message displayed. The vehicle was taken to the dealer, who diagnosed that the coolant pump and water pump were leaking, and the radiator needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure. The manufacturer opened for the failure. The failure mileage was approximately 148,000.

Smart City Break Malfunction warning light appears while driving. Simultaneously the tire pressure warning appears. Also, at the same time, the temperature reads -20 to -40 degrees. Yes, vehicle is available for inspection. Fearful that car could randomly break while driving putting myself and family in danger since there is a malfunction. Mazda service center says the problem can’t be reproduced so there’s nothing they can do. The problem seems to appear when the outside temperature is 60 degrees Fahrenheit or higher.

Engine failure with crack in the engine after a loss of coolant fluid.

Head gasket leaking and caused major engine issue at 89,000 miles. Mazda has known of this issue, but refuses to recall it.

While my wife was driving her 2016 Mazda Cx-9 Grand Touring on the freeway, many of the dashboard indicator lights came on warning her the engine was over heating and to pull over immediately. While she was attempting to move over to the shoulder, smoke appeared from underneath the engine hood which made it difficult to safely move over to the shoulder. She believed the car was on fire so immediately exited the vehicle along with her sister whom was pregnant. I arrived within minutes and noticed the engine compartment was smoking and coolant/engine oil leaking underneath the car. The car was towed to my local Mazda dealership where I was advised days later the engine needed to be replaced due to blown head gaskets. They advised the vehicle over heated causing oil and coolant leaking from cylinder head that is warped. This repair would cost $11, 179.29. Mazda service advisor also mentioned the radiator and lower/upper radiator hoses needed to be replaced. This repair would cost $2691.28. This incident could've resulted in serious injuries or death from a known issue with these engines by Mazda. It's only a matter of time before this failed engine turns into a fatality. Do the right thing Mazda and fix these engines. Your reputation is on the line.

Sudden and dramatic loss of engine coolant. Received a warning that engine was overheating, and to shut off engine. Quickly obeyed the prompt and found that most of the engine coolant had been lost due to a catastrophic failure of either the head gasket or head itself.

Vehicle failed to turn off the engine while in park and I was unable to lock vehicle while engine was still running. The ignition button failed to work.

Cylinder head coolant leak. No warning lights.

1. What component or system failed or malfunctioned, and is it available for inspection upon request? The entire electrical system is malfunctioning. All dashboard service lights (check engine, ABS, etc.) illuminate simultaneously, causing the vehicle to stutter and shut off while driving. The vehicle is available for inspection. 2. How was your safety or the safety of others put at risk? This issue has resulted in a dangerous situation, particularly when the vehicle lost power on the highway with my young children aboard. This sudden loss of control could have led to a severe accident. 3. Has the problem been reproduced or confirmed by a dealer or independent service center? Mazda’s service department has not been able to reproduce the problem despite multiple visits. I have provided video evidence, but no conclusive diagnosis or resolution has been achieved. 4. Has the vehicle or component been inspected by the manufacturer, police, insurance representatives, or others? Mazda’s authorized technicians have inspected the vehicle several times, but no substantial action has been taken. The vehicle has not been inspected by police or insurance representatives. 5. Were there any warning lamps, messages, or other symptoms of the problem prior to the failure, and when did they first appear? All dashboard lights come on simultaneously without prior warning. The symptoms have been random and intermittent over the past few months. Given the ongoing risk, I request an immediate replac

August 2nd I noticed a smell of Coolant coming from my car. I looked under my car and noticed it leaking green coolant. I took it to Mazda where they had it for 7 days to then give me a $6,300 estimate with possible added expenses. They diagnosed it as a cracked cylinder head and needs a gasket as well. I am a single mother and have work but I cannot afford that repair especially since Mazda is not going to honor there vehicle and what they stand by. With this issue with the coolant leak and the cracked cylinder the vehicle could have overheated and go into limp mode and come to a sudden stop with my children in the car while driving on the road. I could be hit as this puts my family at risk of injury while we go to school or work. Mazda has done nothing but tell me to submit a claim with customer service which I have. I had my case manager call me once and left a voicemail and I have called multiple times and have not heard back. There was no warning of this until I found forums and other stories that this unfortunately has happened to hundreds of Mazda owners.

Coolant sprayed on top of engine

Our 2016 Mazda CX 9 began leaking coolant and we took it to a shop who diagnosed it as coming from the cylinder head, requiring a very expensive repair or new engine. Luckily our engine did not sieze up while driving, but it easily could have with our baby and toddler in the car. Upon searching the internet I found countless reports from other CX 9 owners who experienced the very same issue at similar mileage ~50k-70k. There is a technical service bulletin for this issue, but they have not issued a recall. This very expensive repair is going to set us back significantly and is a financial burden we were not expecting from our well cared for vehicle. It seems Mazda knows about the issue and is unwilling to address it.

The contact owns a 2016 Mazda CX-9. The contact stated while driving at an undisclosed speed, the check engine warning light illuminated, and the vehicle started shuddering and overheating. The vehicle was taken to an independent mechanic who diagnosed the vehicle and determined that the failure was related to a cracked head gasket. The vehicle was not repaired. The contact related the failure with the Technical Service Bulletin: 01-03/21; however, the vehicle was not included. The manufacturer was not notified of the failure. The failure mileage was approximately 92,000.

Cracked cylinder head causing coolant to leak.

2016 Mazda CX-9 is leaking coolant from exhaust side of engine cylinder head. This issue has been confirmed by a Mazda dealership in North Charleston, South Carolina. The issue first appeared shortly after replacing the water pump (performed by the same dealership). The issue is known and documents on Mazda TSB 01-002/23 - COOLANT LEAKS AT CYLINDER HEAD. The safety of my family was put at risk as there was no indication of a cracked head until there was coolant leaking on the driveway. Should the car have overheated without the indication of a coolant leak, the car would have been placed in to limp mode. Prior to the leak, there were no warning lamps or messages indicating the issue. Further, the Mazda dealership did not detect the issue at the time of replacing the water pump.

The contact owns a 2016 Mazda CX-9. The contact stated that while driving at an undisclosed speed, the vehicle stalled. Several unknown warning lights illuminated. The contact stated after the vehicle cooled off, the was able to be restarted. The contact checked under the vehicle and stated that there was coolant leaking on the ground. The vehicle was taken to an independent mechanic, where it was diagnosed with a coolant leak behind the engine. The vehicle was not repaired. The contact related the failure to Technical Service Bulletin: 01-002/23. The dealer referred the contact to the manufacturer for assistance. The contact was unable to reach the manufacturer for assistance. The failure mileage was unavailable.

Vehicle had a horrible coolant leak at the rear of the engine to find out the engine has a weak cylinder head and is known to break and leak coolant. The vehicle will need a new cylinder head or engine replacement.

A month ago, I experienced a coolant leak at the back of the engine compartment. Upon researching I found that the head was prone to crack at the turbo and produce the leak. I took to my dealer, and they confirmed that it was in fact a cracked head causing the coolant leak. They also confirmed it was a known Mazda problem on the 2016 and newer 2.5 liter turbo engines. The dealer fixed four in the last month and one on a car their salesman purchased that the head failed at only 2000 miles. I was quoted a cost of $5965 for cylinder head replacement. It seems extremely excessive for a new cylinder head and a more appropriate price for a completely new motor. If this is a known defect on this motor no matter the miles, it seems Mazda should correct this problem in or out of warranty.

Engine head cracked. Known problem with a tsb issued

My car has a cracking cylinder head and is leaking coolant.

2016 Mazda CX-9 2.5L Turbo Touring with 93,197 miles. In September of 2022, I noticed a sweet smell coming from the engine bay after coming home from work. I took my car to my mechanic on 9/30/2022 for an oil change and asked if they could figure out the "sweet smell" coming from the engine bay. When they were doing the oil change, they checked for leaks and noticed that coolant was leaking from cylinder head. Since it was out of warranty, I had my mechanic repair the issue. Which resulted in a complete cylinder head replacement. This is a know issue by Mazda and there is lots of documentation online for this as well. There has since been updated parts to repair this issue, but this should be a recall covered by Mazda. Cause this repair cost me $5,700 out of pocket.

My seat warmer caught fire and burnt a hole through the seat.

We noticed anti-freeze leaking from our car a couple of days ago and immediately brought the car to our local mechanic. The mechanic determined that one of the cylinder heads in the engine was cracked and was leaking anti-freeze. He said the car was unsafe to drive. He also told us that a TSB had been issued by Mazda for this problem ( Bulletin No 01-002/23, issued 02/10/23). This bulletin states "Residual stress generated during production in the cylinder head material may be greater than expected. The external force from the exhaust system when driving over bumps may cause unexpected force to certain areas of the cylinder head". Had we not noticed the leak, the engine could have overheated, causing the engine to seize at any time, any place. which could have led to a dangerous accident. An accident that could have occurred on a major highway and could have involved other vehicles as well. Our car has just under 80,000 miles, has been well maintained and garage kept. I do not understand why a manufacturing defect such as this - which could lead to engine failure is not a mandatory recall by the manufacturer. We should have been warned that this could happen and mazda should be responsible for the cost of the repair. It is an engineering design flaw of the vehicle!

I started smelling coolant after exiting the vehicle from a drive. Coolant level was very low. Adding coolant did not last long. I could not see where the leak was. The dealership evaluated and determined I had a cracked cylinder head and the car is leaking coolant near the rear of the engine. This could cause the engine to seize should coolant get into the engine. The dealer (New Rochelle Mazda) explains the cylinder head needs replacing. The dealer also observed bad rear sway bar links. One was detached. The car is serviced at the same dealership every 5k miles. The car has approximately 85k miles. The cylinder head has been repaired by the dealer under the extended warranty. Safety risk was moderate as the car could have stalled on the highway. The component was inspected by the warranty company and dealer only. The only warning lamps that showed up once were both brake indicator lights came on and the climate control would not warm the car.

Vehicle “surges” at idle. 300-500 RPMS at a time. Sometimes the brakes hold and sometimes not. Have nearly been in 3 collisions the last 2 days because of this issue. The ECM codes indicate throttle body or TPS issue, both of which have been unfounded. Vehicle has 63,000 miles. Researching this topic online found that many others have had this issue with no associated safety recalls noted. I am hoping to bring light to this so someone doesn’t have to be injured or killed to have this rectified.

Cylinder head had a crack in it and had to be replaced.

The car started to overheat so we added coolant and then the car started to stall had our mechanic look at it and he said the head gasket needs to be replaced. How is this not a recall

The intercooler failed or failed cylinder head causing coolant leaking into the exhaust side and cause the engine to over heat.

Engine is leaking coolant. Took the car to Horne Mazda of Avondale dealership for inspection, was told coolant is leaking from cylinder head. Was told the engine overheated and both cylinder head and cylinder block warped and will need to replace the engine. I feel my safety and others were at risk because the car could have lost power and stalled in the middle of roadway at any time due to there was no symptoms of my car engine overheated, car was running as normal, no check engine light, coolant temperature gauge did not show it was overheating, no sign of engine loosing power, no smoke from under the hood, no sweet smell or any indication engine is loosing coolant and overheating while driving. It appears to be a slow leak because coolant reservoir still have coolant above minimum level. First sign of coolant leak was notice during first week of October 2023 when small amount of green fluid was found on garage floor, took car to dealer on Oct.12.2023 for inspection. MazdaUSA refused to cover engine replacement under paid Mazda Extended Confidence warranty (MEC), blaming it's owners fault for operating car while engine overheated and refused to provide written copy of inspection details.

The vehicle has tire pressure monitoring system malfunction warnings and parking brake malfunction warnings even after taking to dealership to be fixed. Was told it’s a known problem by Mazda, should be recalled, but there were not any current recalls for the issue.

While driving, engine suddenly overheated due to coolant leak from cracked cylinder head. This was a known issue per the TSB 01-002/23. See attached. Vehicle only has 55k miles and has been maintained, only requiring oil change, topping off of fluids, and filter changes. Dealership has determined that it will require a completely new long block. Mazda USA is currently only willing to cover a small fraction of parts costs, requiring me to pay the remaining parts and all labor costs.

Car started running rough and losing power intermittently. After arriving home and parking the car, a puddle of coolant started at the rear of the engine. Online research indicates this is a known issue for the 2016 CX-9. Head gasket failure causes coolant leak from back side of engine at the head gasket. Coolant is still leaking 24 hours later without the car being run.

I have taken the Mazda CX9 since I bought it new to service at Mazda every 6 months or 5,000miles as suggested. Two years a new engine was required due to overheating and coolant problem which the service man noticed 5 months prior during service appointment but didn’t suggest doing anything. Now two years later new engine they installed overheated also.The Mazda has never been in a wreck of any sort. The Mazda has 86,000 miles on it only. How can a car have 2 engines fail in 7 years when it has been serviced there at the agency punctually as required?

Coolant leak. Needs new motor to fix issue.

The car has 75K miles on it and has always been maintained by either Mazda or independent garages. Engine overheating, took car to Mazda specialist and found the engine cylinder head is cracked. This is a known issue with this type of Mazda engine and Mazda has published a TSB which I attach. Car is unsafe to drive as coolant may leak completely at any stage and leave myself and family stranded. The cost of the fix exceeds $6,000!

As I am accelerating to merge onto the highway from an on-ramp, while the gas pedal is depressed, I will get a series of sensor alerts simultaneously (city brake malfunction, park assist malfunction, lane assist malfunction, etc.) and my gas pedal becomes non-functional at 60-70mph. It is terrifying especially when there is other traffic around my vehicle. This exact issue has happened 6 times within the past 12-18 months at seemingly random intervals but always when I am accelerating onto the highway at 50-70mph. I typically pull off to the side of the highway and turn off the vehicle. After letting it sit off for ~30 seconds, I turn the vehicle back on and all of the sensor alerts have cleared and the vehicle functions properly including the gas pedal and I am able to rejoin the highway. I took the car to the Mazda dealership in my state of Vermont a few months ago to have them diagnose and address the problem. They had never heard of this issue and were unable to find the root cause or fix it. Please help, this is dangerous!

I just had my engine replaced due to a cracked cylinder head that allowed coolant to leak into cylinder #3 & #2.

Crack cylinder head

Cylinder head crack/failure required the replacement of the entire engine on my 2016 Mazda cx9, the odometer was only at 85,000km. The crack Resulted in loss of coolant and overheating, the indicator on dash stating to pull over and shut the car off. This could have resulted in engine seizing if I was unable to safely pull over. This is a know issue by Mazda, the dealership has seen this issue before, there is lots of documentation online for this as well. There has since been updated parts to repair this issue, This should be a recall covered by Mazda. No car should require an entire engine replacement at 85,000km. This repair cost me $7700 out of pocket.

First radiator blew (after noticing the temp gauge higher than normal and fan running a lot), and when replaced, the 2016 Mazda CX-9 continued to leak coolant. Took it to dealership to find out engine cylinder cracked and head gasket. A simple google search finds that so many Turbo Mazda’s between the years of 2016-20 experienced this design flaw as well. Mazda would not cover any of it since the car was out of warranty. It costed me over $7,000 to repair radiator and engine.

My 2016 Mazda CX-9 2.5l Touring has approx 67,500 miles. I noticed the "sweet" smell of coolant after driving. The temp gauge was not showing signs of overheating. I checked under the hood and coolant level in radiator and reserve tank were normal. I also did not see any coolant leak/patches under the car. Few days later the car temperature gauge shot past the 1/2 mark. i stopped the care let it cool and checked under hood. radiator was empty but reservoir tank was still full. there were signs of coolant drips underneath car on the plastic cover below the area of the water pump (passenger front wheel side). waiting to have car assessed/fixed by mechanic.

UKNOWN-Seat Heating system in my car gets too hot to the skin where it burns the skin if not turned off. I’m not able to use it often because even on low setting it gets extremely hot.